1. Field of the Invention
The present invention in particular relates to a glass ceramic composition capable of being fired at about 1,000° C. or less, a glass ceramic sintered material produced by firing the same and a ceramic multilayer substrate using the same.
2. Description of the Related Art
In recent years, the performance of electronic components has been significantly improved in the field of electronics. In particular, regarding information processing equipment typified by mobile communication terminals, personal computers and the like, which support an information-oriented society, the increase in information processing speed has accelerated. Consequently, the so-called multichip module (MCM) has become commercially practical as an electronic component for performing high-speed information processing. In the MCM, semiconductor devices, e.g. LSIs, are mounted at a high density on a ceramic multilayer substrate.
It is desired that the resistivity of a wiring conductor provided between LSIs in such a module is minimized in order to process faint, high-speed signals. Examples of low-resistivity conductors include, for example, silver and copper. As a material for the substrate, a material capable of being simultaneously fired with the low-melting metal, specifically, a material capable of being fired at about 1,000° C. or less, is required, and a glass ceramic composition composed of alumina and borosilicate glass and the like is widely used.
Various composite multilayer substrates have been studied in order to match trends toward further miniaturization and higher frequencies with respect to ceramic multilayer substrates. For example, in Japanese Unexamined Patent Application Publication No. 12-264724, a composite, laminated ceramic electronic component which was constructed by laminating a low-dielectric-constant layer and a high-dielectric-constant layer was proposed. The low-dielectric-constant layer was provided with wirings or equipped with semiconductors and the like, and the high-dielectric-constant layer constitutes a capacitor, resonator or the like.
Regarding the above-mentioned multilayer substrate including a composite of the high-dielectric-constant layer and the low-dielectric-constant layer, the occurrence of cracks and warps in the substrate during the firing must be reduced by decreasing the difference between the thermal expansion coefficients of the layers having the respective dielectric constants. However, the thermal expansion coefficient of the above-mentioned glass ceramic composition composed of alumina and borosilicate glass was about 7 to 8 ppmK−1, whereas the thermal expansion coefficient of a conventional high-dielectric-constant material was about 10 ppmK−1. Therefore, the above-mentioned problems of cracks and warps in the substrate were not able to be overcome.
Conventional dielectric materials, e.g. TiO2, SrTiO3 and CaTiO3 had high dielectric constants and high Q values. However, the temperature coefficients of dielectric constants were large negative values, and therefore, changes in characteristics of the ceramic multilayer substrate due to ambient temperature changes were not able to be avoided.